Types of Metal that can be Powder Coated;
A question that is often asked is; Can any metals be coated? The answer is yes, the only exception that comes to mind is of course Mercury! Steel, Aluminium, Brass, Copper,Zinc, Cast Iron, Castings of various metals. They all have various factors that should be considered before Powder Coating. The main overriding factor is the condition of the surface, does it have any sort of corrosion or residues from previous processes it may have undergone prior to being coated?
It is true to say that the majority of corrosion issues occur because of ‘something’ on the surface of the metal that affects the longevity & corrosion resistance of the part.
Steel; must be free from rust and mill scale found on hot reduced material such as angle iron and joists. The best process for achieving this is to shot blast the parts. The recognised specification for this is S.A 2.5 which in simple terms is very through shot or grit blasting.
Aluminium; on contact with air, forms an oxide layer on the surface. Depending upon the specification and corrosion resistance required consideration should be given to removing this prior to Powder Coating. This can be achieved by light shot blasting, etching the aluminium in a mild acidic solution, chromate pre-treatment or flash hard anodising. All of these will improve the durability and corrosion resistance of the Powder Coating.
More on aluminium powder coating here.
Cast Iron parts; These should be free of scale or residues from the casting process. The ideal pre-treatment is shot blasting.
Brass & Copper; these can be Powder Coated. The only issue with some grades of brass and copper is that when coating in light or pastel shades a staining can occur which bleeds through from the surface. Thorough cleaning is a must and experimenting with various powder types and cure temperature.
Castings; Aluminium and Zinc castings can be powder coated. They can be Sand Castings, Gravity Die Castings or Die Castings. As long as the surface is clean and free from residues remaining after the casting process then the Powder Coating will provide a corrosion free finish. The one big issue with castings is Porosity. When the hot metal is poured into the mold or die turbulence is caused and this can leave traces of air rather like bubbles in an Aero Bar. This air trapped in the metal can with the application of heat during the curing process cause small bubbles to appear in the surface of the coating. The remedy to this is to lower the cure temperature and use what are called ‘Low Bake Powders’. Also pre-heat the castings prior to coating so that as much as possible of the air in the casting is expelled.
In summary, most metals can be coated but the quality of the coating depends less on the metal than what is on the surface prior to Powder Coating. We serve in a range of areas to suit your needs, including offering different services including powder coating & masking.